The present invention relates generally to molecular and developmental biology and more specifically to methods of modulating gene expression and influencing cellular differentiation.
The expression of cell type-specific genes depends on both positive and negative gene expression controls, which are implemented throughout the developmental history of cells. Numerous genetic studies have provided evidence that cell type-specific activators and repressors of gene expression are essential components of the process. In addition to the conventional transcription machinery, gene expression control by small non-coding RNAs, at the post-transcriptional step, also appears to be essential to the regulation of gene expression. Non-coding RNA genes, which produce transcripts, can function directly as structural, catalytic or regulatory RNAs, rather than expressed mRNAs that encode proteins. Plants, flies, worms, mice and humans harbor significant numbers of small RNAs likely to play regulatory roles. Although most of the identified non-coding RNAs have unknown function, their sequences are typically conserved among different species, and many have intriguing expression patterns in different tissues or stages of development, pointing towards a general role for non-coding RNAs in modulating gene expression during development, such as tissue-specific patterning and cell fate specification.
The mammalian nervous system is composed of a remarkable number of different types of neurons and glia. While it has become clear over the past several years that specific genes control cellular differentiation, the molecular mechanisms by which neuron-specific gene expression is regulated in the central nervous system remain a focus of study. The regulatory mechanisms of gene expression that determine a stem cell's fate with regard to giving rise to a particular lineage remain largely unknown. Genes involved in regulating mammalian neural differentiation are just beginning to be discovered. Some important regulators identified to date include NeuroD, NeuroM, neurogenin, and the neuron restrictive silencing factor (NRSF).
Many of the genes important for neuronal differentiation and maintenance contain neuron-restrictive silencer element/Repressor Element 1 (NRSE/RE1) sequence, which is recognized by the protein neuron-restrictive silencer factor (NRSF), also known as RE-1 silencing transcription factor (REST). The maintainance of neuronal gene repression in non-neuronal cells depends on the ability of NRSF/REST to bind the NRSE sequence. To repress gene expression, NRSF/REST recruits negative transcriptional regulators such as HDACs and methyl-DNA binding proteins. Multipotent adult neural stem cells switch from actively repressing neuron-specific genes in the “stem cell state” to actively expressing neuron-specific genes in the “differentiated state” allowing the cell to proceed to become a neuron, a process that involves de-repression in order to activate transcription of genes having an NRSE. The mechanisms controlling the switch from active transcriptiponal repression to de-repression of neuron-specific genes are of great significance to the determination of cell fate.
Given the cellular diversity of the nervous system and the complexity of the underlying genetic mechanism, the understanding and treatment of nervous system disorders presents a unique challenge. The elucidation of the mechanisms that regulate the development of the nervous system and ability to modulate the regulation of genes that coordinate nervous system development is an important goal and will provide valuable information regarding the the causes and potential treatments of neurological and neurodegenerative disorders.
Thus, there exists a need to understand the processes that orchestrate gene expression within regulatory networks that coordinate cellular processes such as differentiation; to elucidate the molecular components involved in these processes; and to develop therapeutic tools for influencing cellular processes such as neuronal differentiation. The present invention satisfies this need and provides related advantages as well.